The M18 Colored Smoke Grenade is designed and produced by the United States Army. It was introduced in 1942 during World War II, eventually replacing the M16 Colored Smoke Grenade. Since then, it has been the primary colored smoke grenade for the United States Armed Forces. It is used as a ground-to-ground or ground-to-air signaling device, target or landing zone marking device, or for screening unit movements.
The M18 was developed in 1942 during World War II and was completed in November of that year. It was designed to replace the M16 smoke grenade, which did not burn as long or as vividly. It was designated standard issue in the fall of 1943. Both were produced at the same time as the M16 production lines were already setup when the M18 was adopted.[citation needed]
The M16 was available in red, orange, yellow, green, blue, violet, and black. The M18 initially were going to be produced in the same colors, including white, but it was decided to limit it to four colors (red, yellow, green and violet) for simplicity. The M16 was declared limited standard in 1944 but was still available when it was declared obsolete in the early 1990s.[citation needed]
During the Vietnam War, the M18 was mainly used by troops for signaling to helicopters and other aircraft. Red typically meant danger, while violet and yellow were used to mark pickup zones and friendly force locations. Green was rarely used due to it being difficult to spot.[1][2][3] However, color coding and usage varied by squad.
In 1971, a non submersible version of the M18 was under testing as the M18 provided poor signal when used in areas partially or fully covered in water. This made the standard M18 ineffective in such areas in Vietnam. This version of the M18 had a silicon ballute which acted as a parachute and flotation device. It was produced by Northrup Carolina, a subsidiary of Northrup Grumman at the time.[4][5]
By June 2019 the Pine Bluff Arsenal has produced 3,888,502 M18 grenades since its introduction.[6]
In 2022, the US supplied Ukraine with an undisclosed amount of M18 smoke grenades as part of a military aid package.[7][8]
Usage
United States Army infantryman throws an M18 smoke grenade for training (2025)
The M18 is used by holding it in one hand with the safety lever pressed against the canister. The safety pin/ring is then removed after which the M18 can be thrown. As the safety lever is released, it is forced away from the body by a striker spring. The striker rotates on its own and strikes the percussion primer. The fuze delay then starts the ignition process. The tape covering the bottom emission hole is blown off and smoke is released. After ignition, the M18 produced a cloud of colored smoke for 50 to 90 seconds. The M18 could be thrown up to 35 meters by the average soldier.[9]
If the fuze was non-functional, the M18 could still be used. This was done by removing the tape covering the hole on the bottom, removing the fuze assembly, and igniting the starter mixture with an open flame.[10]
With the M18 there is a danger of starting a fire if it is used in a dry foliage area as the inside of the tube gets very hot during the burning process (upwards of 350°C).[11] Expended smoke grenade canisters remain hot for some time after burning out and should not be picked up bare-handed.
Launcher Attachments
Diagram of the M2A1 adapter with the AN-M8 smoke grenade.
The M18 was able to be used as a rifle launched grenade using the M2/M2A1 (originally designated T2E1) chemical grenade projection attachment.[12] This attachment was mounted onto a M7A3 or M76 grenade launcher, which went onto a rifle or carbine such as the M1 and M14.[13] It was a modified version of the M1 grenade adapter and was created around 1944.[14]
The M2 adapter consisted of a stabilizer which was a metal tube with a solid fin assembly on one end and a base plate with a set of three claws on the other. The grenade was installed by being forced down into the clips until held securely in place. A setback band, which was a metal band with the ends held together by a spring, was installed midway on the grenade with the spring over the safety lever to hold it against the canister.[15][16] The M2A1 was a revised design with a slotted fin assembly and reinforced base plate which gave it more stability.[12]
To use the launcher, the stabilizer was installed over the grenade launcher at a position that would give a desired range. The grenade/adapter was rotated so that the safety lever faced the ground, and the safety pin was removed. The assembly was launched by firing a high-powered blank from the rifle. When fired a forceful shock causes the setback band to slide down the grenade, releasing the lever. After launching the assembly would remain attached to the grenade until it landed. Using the M2/M2A1 adapter allowed higher ranges up to about 180 meters.[15][17]
The M2/M2A1 launchers were not widely used for the M18, which were intended more for chemical grenades such as the M6/M7 tear gas grenades. The impact of hitting the ground using the adapter could cause the M18 to burn out prematurely.[15] There were rifle launched smoke grenades such as the M22 series available in the same colors that were designed more for this purpose.[18]
A modified version of the M2A1 designated T1 was made for suspending M18 smoke grenades from trees to increase visibility. Instead of a setback band it used a solid ring to hold the grenade safety lever. A cardboard tube that contained rayon cord was tied to both the base of the T1 and another ring positioned around the top of the grenade. When the rifle was fired the entire assembly was launched, with the setback ring sliding down and striking the clips holding the grenade. This would release the safety lever and clips, separating the grenade and adapter assembly. As the grenade flew, the cord would unravel from the tube which could easily be entangled in trees and allow the grenade to be suspended.[14][18]
Design & Variants
The M18 comes in four variations: G940 (Green), G945 (Yellow), G950 (Red), and G955 (Violet).[19]
Diagram and cross section of the M18 Colored Smoke Grenade.
The early M18 was a 2.50" wide and 5.75" tall thin steel cylindrical tube with a M200A1 pull-ring fuze assembly screwed into the top.[20] It had 4 emission holes on the top surrounding the fuze assembly and an additional one on the bottom covered by tape for smoke to release when ignited. It was light gray, with the top of the grenade painted yellow.[21] A yellow band was painted around the body along with yellow text stating the color, lot number, and date produced following MIL-STD-1168. Including filling, it weighed 19 oz.
The body contained a pyrotechnic delay column with a primer and starter/ignition mixture surrounding the hole the fuse assembly goes into. Below that is a donut shaped smoke filler mixture that varied in composition depending on the color used.[22] It came shipped in a metal tube to protect it from the environment during shipping.
Yellow M18 from January 2012 with shipping tube.
In the 1950s the M18 was 2.50" wide and 4.50" tall. It had a M201A1 pull-ring fuze assembly. There were 6 emission holes on the top and an additional on the bottom covered by tape for smoke to release when ignited. The top was painted indicating the color with a yellow band and text on the body.[23]
In the 1960s the M18 was largely similar to the original, being 2.50" wide and 5.75" tall with the same hole arrangement. It came in an olive drab body with the top painted indicating the color. A yellow or gray band and text were painted on the side stating the color, lot number, and date produced following MIL-STD-1168.[24] It came shipped in a waxed cardboard tube to protect it from the environment during shipping.
In 2005, the top 4 emission holes were removed leaving only the bottom one. Inside starter patches were put between pucks of dye to improve burning time and performance.[25][26] The design was otherwise the same as the previous iteration.
Non-submersible Variant
The non-submersible M18 was the same size as the standard M18, being 2.50" wide and 5.75" tall, and looked basically identical. The body contains a chimney design vent hole under the fuze in the middle. Surrounding the chimney is a folded silicone fiberglass ballute that is attached to a bulkhead plate. 8 vent holes on the top of the bulkhead are used to inflate the ballute when the grenade is ignited. Below the bulkhead is a starter/ignition mixture, inflation mixture, and smoke mixture.[27]
When ignited and thrown, the top of the grenade with the pull-ring fuze assembly detached while the ballute inflated. The grenade would then glide towards the ground upright, and could float in water.[27] It was found these versions of the M18 had a lower smoke volume but burning time was almost double the standard M18 with 90 seconds minimum.[27]
Although testing was considered successful, this version of the M18 was never used outside of it. It was created as the standard M18 provided poor visibility for signaling when used in areas partially or fully covered in water in Vietnam.
Chemistry
The smoke from an M18 is produced by volatilizing and condensing a colored dye mixture. The heat produced by the starter mixture volatilizes the dye which is then condensed by the air forming a colored smoke cloud.[28] A cooling agent is added to the smoke mixture to help prevent excessive decomposition of the dye while burning time can be regulated by adjusting the amount of oxidant and combustible materials.[29]
In the original M18 chemical components, sulfur was used for the starter mixture with sodium bicarbonate as a coolant. Dye mixture was dependent on the color of smoke being produced.[29] During extensive testing in the 1980s, it was found that the burning of the chemical components caused the smoke to be toxic so the formulas were remade.[29]
M18 without burning patches (left) and with them (right).
The new formulas used sugar for the starter mixture and magnesium carbonate as coolant.[29][28] The dye mixtures were also changed, using different coloring components. The formula for the green and yellow M18 were changed quickly with relative ease, while red and violet were more challenging to produce. Early attempts with red and violet failed due to excessive flaming and insufficient smoke production of the mixtures. For violet it was also found the new mixture using Disperse Blue 3 for smoke coloring was even more toxic than the original. This was later changed to Disperse Red 11.[30]
Red and violet M18's retained the original formulas until the early 2000s, where they were looked at again by the Environmental Security Technology Certification Program (ESTCP). The introduction of wafer starter patches between dye pucks improved flaming and burning times, making the new formulas more successful.[30] The new red was found to produce a pinkish smoke rather than the intended darker red, caused by added Terephthalic Acid. Several attempts were made to correct it but were unsuccessful.[31]
The smoke produced by an M18 is harmful if inhaled, even with the new less toxic smoke mixtures. In enclosed spaces the grenade displaces oxygen and produces carbon monoxide due to the burning process. It can cause respiratory problems or oxygen deprivation.
[33] - Toxicity of Military Smokes and Obscurants: Volume 3
[34] - Demonstration of the Replacement of the Dyes and Sulfur in the M18 Red and Violet Smoke Grenades
Manufacturing
General Brig. Gen. Michelle Letcher chatting with Pine Bluff Arsenal M18 production workers (2019).
The Pine Bluff Arsenal in Arkansas is the only manufacturer of the M18 today.[35] It has been assembled there since its introduction in 1942.[6] Majority of M18's were produced by Pine Bluff. This is denoted on an M18 by a "PB" before the lot number marked on the outside. The various components of the M18 are made by different manufacturers contracted yearly in the United States. As of 2024 the body and lid are made by Tool Masters, Inc. in Tuscumbia, Alabama. The fuze assembly is made by Day & Zimmermann in Texarkana, Texas. The smoke mixture dyes are produced by Nation Ford Chemical in South Carolina.[36][37][38]
During the Vietnam War other manufactures such as Martin Electronics, Inc. ("MEI") from Florida and Talley Industries, Inc. ("TAC") from Arizona were used.[39][40][41] Ordnance Products Inc. ("OPI") from Maryland also produced the M18 in limited quantities before being acquired in 1969.[41][39]
↑ Cooke, Gary (22 April 2007). "Hand Grenades". Gary's U.S. Infantry Weapons Reference Guide. Archived from the original on 6 March 2025. Retrieved 29 March 2025.
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